Surgical fasteners, including clips and staples, and methods of applying these fasteners are well known in the art. Surgical fasteners can be used to close incisions or wounds, or to clamp vessels or ducts to prevent fluid flow. Surgical applicators used to apply these fasteners comprise various designs depending on the use to which the fasteners are employed. For example, a clip applicator is typically a pistol-shaped vise used where a vessel or duct must be sealed. The clip is directed to the location of application and then the vise secures the clip, collapsing and sealing the vessel. A surgical stapler is typically used where an incision or wound must be closed. A surgical stapler typically employs an anvil to form the fastener during application. With increasing use and improvement of various surgical applicators, fasteners have also improved. Some examples of surgical fasteners are found in U.S. Pat. Nos. 4,407,286; 4,489,875; and 4,932,960.
In the '286 patent, Noiles et al. disclose a surgical staple which is designed to reduce the tendency of the staple to slip off the anvil during application or to adhere to the anvil after application. In the '875 patent, Crawford et al. disclose a self-centering staple to remedy the problem of misalignment of the staple during application. In the '960 patent, Green et al. disclose a bioabsorbable fastener designed for elastic expansion to prevent breakage. Although the foregoing surgical fasteners, as well as others known in the art, have addressed and remedied many problems encountered with the use of these fasteners, there still exist problems accompanying their use.
One such problem is the slippage of fasteners at the point of their application in the tissue. During surgery it is frequently required to shut off fluid transfer to areas, thus fasteners are often placed around blood vessels or other structures to achieve this. For example, in cases where polyps are to be removed, fasteners are typically applied to the base of the structure to shut off fluid transfer and the polyp is removed. The fastener is left in place during the healing process to prevent fluid loss. As hydrostatic pressure increases due to the blockage, fasteners tend to slip away from the pressurized area which can result in fastener displacement and fluid loss or hemorrhage. Another problem seen with currently used fasteners concerns the closure of the fastener itself. During application of the fastener, the typical U or V-shaped designs often result in non-uniform closure of the fastener over the vessel, which again can lead to fastener displacement as well as fluid loss or hemorrhage. To avoid these problems, the fastener is tightly fastened into the tissue encompassed by the fastener, which still does not guarantee against slippage. In addition, in surgeries where fasteners are employed to temporarily shut off blood flow through a vessel, this form of application can cause irreparable injury to the vessel.
From the foregoing it may be seen that a need exists for an improved surgical fastener which is designed to resist displacement once secured to the tissue.